| Clue | Source | Date |
|---|---|---|
| Bluish discolouration of the skin, a sign that the blood needs oxygen | Irish Times Simplex | 22 Mar 2022 |
| Bluish discolouration of the skin, a sign the blood needs oxygen | Irish Times Simplex | 09 Mar 2021 |
| Bluish colouration of skin due to poor circulation | The Times Concise | 11 Apr 2020 |
| Any wrinkling in lettuce is a result of oxygen deficiency |